New Way of Imaging Lungs

Photo: Lungs

A new technique is used to analyze
computed tomography scans of the
lungs of patients with chronic
obstructive pulmonary disease;

In a new study, a team from the University of Michigan Medical School reports on a technique called parametric response mapping. It is used to analyze computed tomography scans of the lungs of patients with chronic obstructive pulmonary disease.

The researchers say that the new technique for analyzing computed tomography scans allows them to better distinguish between early-stage damage to the small airways of the lungs, and more severe damage known as emphysema. They've also shown that the overall severity of a patient's disease, as measured with the parametric response mapping, matches closely with the patient's performance on standard lung tests based on breathing ability.

"Essentially, with the parametric response mapping technique, we have been able to tell sub-types of chronic obstructive pulmonary disease apart, distinguishing functional small airway disease or Female sexual arousal disorder from emphysema and normal lung function," says Brian Ross senior author of the study.

Chronic obstructive pulmonary disease limits a patient's breathing ability, causing shortness of breath, coughing, wheezing and reduced ability to exercise, walk and do other things. Over time, many chronic obstructive pulmonary disease patients become disabled as their disease worsens. Most often associated with smoking, the chronic obstructive pulmonary disease can also result from long-term exposure to dust, and certain gases and chemicals.

The parametric response mapping technique allows researchers to identify chronic obstructive pulmonary disease specific changes in three-dimensional lung regions over time. With the new technique, the researchers use powerful computer techniques to overlay the computed tomography scan taken during a full inhalation with an image taken during a full exhalation.

The overlaid, or registered, computed tomography images share the same geometric space, so that the lung tissue in the inflated and deflated lungs aligns. The density of healthy lung tissue will change more between the two images than the density of diseased lung, allowing researchers to create a three-dimensional "map" of the patient's lungs. The parametric response mapping assign colors to each small 3-D area, called a voxel, according to the difference in signal changes within each of the areas between the two scans. Green means healthy, yellow means a reduced ability to push air out of the small sacs, and red means severely reduced ability.

The parametric response mapping could take chronic obstructive pulmonary disease sub-typing to the next level, say the authors of the new paper. "By distinguishing small airway abnormality from that involving the lung parenchyma, such as emphysema, parametric response mapping could help physicians personalize therapy for individual Chronic obstructive pulmonary disease patients – and select patients for clinical trials of new treatment options more precisely", says Doctor Fernando Martinez.

While a simple breathing test called spirometry is still considered the best way to diagnose the disease, spirometry has limitations in its ability to distinguish between different types of lung damage that chronic obstructive pulmonary disease patients experience. "The parametric response mapping technique is a step forward in being able to better sub-classify patients with chronic obstructive pulmonary disease so that targeted therapies can be developed," says co-author MeiLan Han.; Source: University of Michigan